Can't say if Star Line has done any actual comparisons, but this comes directly from the the 6 Creedmoor srp brass page:
"As with all types of cases this large with small primer pockets, it will require care in powder and primer selection in cooler temperatures to prevent hang fires. Single-based propellents are generally easier to ignite and a quality primer such as the Remington 7 1/2 BR are recommended."
I've been using 7 1/2 s with CFE223 with good results in the 6Cm, but haven't had a chance to try the load in cold weather.
